1. Field of the Invention
This invention relates to a process for regenerating wastepaper and to the use of hydroxysulfonate salts for removing printing inks from printed wastepaper and/or paper circuit waters.
2. Discussion of Related Art
Today, wastepaper is used in large quantities for the production of, for example, newsprint and sanitary paper. Lightness and color are important quality features for papers of this type. To achieve high-quality papers, the printing inks have to be removed from the printed wastepaper. This is normally done by deinking processes essentially comprising two steps, namely:
1. disintegrating the wastepaper, i.e. fiberizing in water in the presence of the chemicals required for detachment of the printing ink particles and
2. removal of the detached printing ink particles from the fiber suspensions.
The second step can be carried out by washing or flotation (Ullmanns Encyclopadie der technischen Chemie, 4th Edition, Vol. 17, pages 570-571 (1979)). In flotation, which utilizes the difference in wettability between printing inks and paper fibers, air is forced or drawn through the fiber suspensions. Small air bubbles attach themselves to the printing ink particles and form a froth at the surface of the water which is removed by savers.
The deinking of wastepaper is normally carried out at alkaline pH values in the presence of alkali metal hydroxides, alkali metal silicates, oxidative bleaches and surfactants at temperatures in the range from 30.degree. to 50.degree. C. The surfactants, which detach and separate the printing ink particles, are mainly anionic and/or nonionic types, for example soaps, ethoxylated fatty alcohols and/or ethoxylated alkyl phenols (Wochenblatt fur Papierfabrikation 17, 646 to 649 (1985)). JP 61/207686, reported in Chem. Abstr. 106, 121694v, describes the use of aliphatic .alpha.-sulfocarboxylic acids and aliphatic .alpha.-sulfocarboxylic acid esters in flotation deinking processes. According to Russian patents SU 773 174, reported in Derwent 51102 D/28, and SU 717 195, reported in Derwent 72992 C/41, good results in the flotation of printing inks are obtained by treating wastepaper with mixtures containing alkyl sulfonates and soaps.
However, the deinking results obtained with known surfactants are often unsatisfactory. Accordingly, the object addressed by the present invention was to provide a process for regenerating wastepaper which would enable the removal of printing ink from printed wastepaper to be distinctly improved.